Refrigeration system and method

ABSTRACT

An alternative method of operating a refrigeration system of the type normally operated in an absorption refrigeration cycle. When a cooling medium such as water is available at temperatures below a chilled fluid temperature which will satisfy the refrigeration load, the absorption refrigeration cycle is suspended, the supply of heat to the generator being discontinued, and the absorber is operated as a condenser to liquefy the refrigerant vaporized in the evaporator. Means are provided for operating the system in such a manner.

United States Patent Hopkins et al. Feb. 8, 1972 54 REFRIGERATION T M D1 2,718,766 9/1955 lmperatoretal. ..62/79 3,122,002 2/1964 Miner et al..62/476 x METHOD Neil E. Hopkins, York, Pa.; Paul W. Muench, MedfordLakes, NJ.

Borg-Warner Corporation, Chicago, 111.

Aug. 24, 1970 [72] Inventors:

Assignee:

Filed:

Appl. No.:

US. Cl ..62/l0l, 62/476, 62/485, 165/105 Int. Cl ..F25b 15/06 FieldofSearch ..62/10l, 181, 196, 476,485, 62/513; 165/105 56] ReferencesCited 7 UNITED STATES PATENTS 2,244,312 I 6/1 gil ijewton .62/ l 81Primary Examiner-William F. ODea Assistant Examiner-P. D. FergusonAttorney-Donald W. Banner, William S. McCurry and John W. Butcher [57]ABSTRACT An alternative method of operating a refrigeration system ofthe type normally operated in an absorption refrigeration cycle. When acooling medium such as water is available at temperatures below achilled fluid temperature which will satisfy the refrigeration load, theabsorption refrigeration cycle is suspended, the supply of heat to thegenerator being discontinued, and the absorber is operated as acondenser to liquefy the refrigerant vaporized in the evaporator. Meansare provided for operating the system in such a manner.

14 Claims, 1 Drawing Figure l 4 IHI Z30 I BACKGROUND OF THE INVENTIONThe present invention relates generally to a method of and means foroperating a refrigeration system which is normally operated in anabsorption refrigeration cycle, and more particularly, to a method ofand means for operating such a system in an alternative refrigerationcycle when a cooling medium is available at temperatures lower than atemperature of the chilled fluid which will satisfy the refrigerationload.

in a typical absorption refrigeration system a liquid is circulated in achilling coil forming a portion of an evaporator in which a refrigerantis vaporized to abstract heat from the liquid. The liquid thus chilledis conducted to a refrigeration load, such as one or more remotelylocated air-conditioning units, the vaporized refrigerant passing to anabsorber for absorption by a solution having a strong affinity for therefrigerant. The absorbent solution is diluted by the absorptionprocess, and the heat of solution thus generated is removed bycirculating a cooling medium in a cooling coil provided in the absorber.The dilute solution is conducted from the absorber to a generator, whereit is heated to evaporate refrigerant, thereby increasing theconcentration of the solution. The concentrated solution is returned tothe absorber, and the evaporated refrigerant is liquefied in a condenserfrom which it is returned to the evaporator to complete the absorptionrefrigeration cycle. The evaporator and the absorber are maintained atsubstantially lower pressures than the generator and the condenser.Water is frequently used as the refrigerant, the chilled fluid and thecooling medium, a suitable source of heat in the generator being steamor hot water circulated in a heating coil. When the refrigerant iswater, the absorbent solution is typically a hygroscopic brine such asan aqueous solution of lithiumbromide or lithium chloride. It is to benoted, however, that a large number of fluids with widely varyingcharacteristics are suitable for use in absorption refrigerationsystems,

The absorber cooling coil often conveniently forms a portion of acooling circuit which also includes a condenser coil, situated in serieswith the cooling coil, for abstraction heat from the refrigerantevaporated in the generator to reduce it to condensate. The coolingwater is conducted from the condenser coil to a remote location wherethe heat abstracted in the absorber and in the condenser is rejected toambient air, usually the air out of doors. Alternatively, and wherefeasible, the cooling water may be drawn from a body of water such as alake, a stream, an artificial pool or a deep well, and returned thereto,the body of water thus forming a portion of the cooling circuit.

The temperature of the heated cooling water must be so related to thetemperature of the ambient air as to provide a favorable heat-transferrelationship. Since refrigeration requirements are usually greatestduring periods of high ambient temperatures, absorption refrigerationsystems are customarily designed to be operated with correspondinglyhigh cooling-water temperatures, and it has been considered necessaryfor stable operation of the system to provide controls which act tomaintain these temperatures within a substantially narrow range despitediurnal and seasonal fluctuations in the ambient temperature.

On the other hand, a need for refrigeration may arise or continue toexist during periods of relatively low ambient temperatures, althoughthe refrigeration load is usually lighter under such conditions. Duringperiods of extremely low ambient temperatures; for example, during thewinter months in the temperate zones, it would often be possible toprovide cooling water at a temperature actually lower than a chilledwater temperature which would satisfy the refrigeration load, and inmany cases such a temperature relationship could be maintained forextended periods of time. However, as noted above, the cooling watertemperature is conventionally maintained within a relatively high rangeof values at all times. This anomalous condition must be consideredinefficient, if not wasteful, and a number of proposalshave beenadvanced for making use of low-temperature cooling water, whenavailable, to reduce the amount of energy required to' operate thesystem.

More particularly, it has been suggested that the low-temperaturecooling water'might be introduced directly into the chilled watercircuit for circulation to the refrigeration load, the remainder of thesystem being inoperative. However, for optimum rejection of heat, thecooling water is normally brought into direct contact with the ambientair, as by being sprayed through a stream of air, thereby causing thecooling water to acquire substantial amounts of contaminants in'bothentrained and dissolved form. Similarly, liquid drawn from a body ofwater is rarelypure. Whilethe components of the cooling circuit may bedesigned to function satisfactorily in the presence of contaminated ordirty water, the chilled water circuit is ordinarily intended tocirculate relativelypurewater to maintain effective transfer of heat atthe units' representing the refrigeration load, and elements of thechilled water circuit are not readily accessible for cleaning orflushing operations. In some installations for example, components ofthe cooling circuit are formed of a corrosion resistant alloy at thesacrifice of some thermal conductivity, whereas'components of thechilled water circuit are typically formed of a metal such as copperwhich is highly conductive of heat but which has relatively lowresistance to certain types of corrosion.

It has also been suggested that the low-temperature-cooling water andthe water to be chilled might be brought into heattransfer relation in asimple'heat-exchanger. Since only the exchange of sensible heat would beeffected,"however, and since the temperature differential is frequentlyonly a few degrees, theheat-transfer surface wouldnec'essarily beextremely large, with attendant pumping and circulation problems.

In US. Pat. No. 2,718,766, issued Sept. 27, l 5'to Tflmperatore et al.,there is shown and described an air-conditioning apparatus of the typewhich is'normally operated in a vapor-compression cycle but which maybeoperated alternatively with relatively coldcondenserwaterbyeonducting'the refrigerant vapor directly fromthe cooleror evaporator to the condenser; that is, by bypassing the compressor. Anequalizer pipe interconnecting the evaporator and the condenser,together'with an associated control valveymust be provided for thispurpose. A refrigerant "pump and a spray pipe must also be added to thesystemto forwardliquid'refrigerantfrom the evaporator sump anddistribute it over the chilling coil in the evaporator in order toincrease the heat-transfer rate between the refrigerant and watercirculated in the chilling coil. Also necessary are controls whichprevent simultaneous operation of the compressor and the refrigerantpump. A saving in energy is said to be realized during periods in whichrelatively cold condenser water is available, since the compressor isinoperative during such periods.

The apparatus disclosed in the aforementioned patent is entirely unlikean absorption refrigeration system in structure and principles ofoperation, and it is to be noted that the condenser and evaporatorcontinue to function in the customary manner during periods in whichlow-temperature condenser water is used, except that the heat-transferrate is increased in the evaporator by the operation of the addedrefrigerant pump and spray pipe. Operation of the primary source ofenergy put into the system, namely the compressor, is'simplydiscontinued. if an attempt were made to operate an absorptionrefrigeration system in this manner, that is, if the supply of heat tothe generator were simply interrupted and vaporized refrigerant bypasseddirectly fromthe evaporator toihe condenser, the system would cease tofunction without substantial and costly additional measures being taken,regardless of the temperature of the cooling medium inthe condenser.

With these considerations in mind, persons skilled in the absorptionrefrigeration art have for some time sought a'pra'cticable andeconomically feasible way in which to make use of a cooling medium atrelatively low temperatures, when available, in order to take advantageof the saving in energy to be gained by such use.

SUMMARY OF THE INVENTION It is therefore a primary object of the presentinvention to provide a substantial reduction in the amount of energyrequired to be put into a refrigeration system of the type hereindescribed when a cooling medium is available at a temperature lower thana temperature of the chilled fluid which will satisfy the refrigerationload.

It is also an object of the invention to provide a method of operatingsuch a system which will permit utilization of a cooling medium at atemperature lower than a temperature of thechilled fluid suitable forsatisfying the refrigeration load.

It is a further object of the invention to provide an economicallyadvantageous method of, and relatively inexpensive means for, operatingsuch a system when a cooling medium is available at a temperature lowerthan a temperature of the chilled fluid which will satisfy therefrigeration load.

In accordance with the invention the absorption refrigeration cycle issuspended and the absorber is operated to condense refrigerant vaporizedin the evaporator. This is done by removing absorbent solution from theabsorber, circulating the cooling medium in the absorber at atemperature lower than a temperature of the chilled fluid which willsatisfy the refrigeration load, and returning refrigerant condensed inthe absorber directly to the evaporator.

Also in accordance with the invention, there are provided a bypasspassage between the absorber and the evaporator, and a valve associatedwith the bypass passage which may be opened to permit circulation ofrefrigerant condensed in the absorber to the evaporator. In a preferredembodiment of the invention the bypass passage conveniently connects theabsorber with a refrigerant passage already provided in many ex-. istingsystems.

THE DRAWING The FIGURE is a schematic representation of a refrigerationsystem constructed and adapted to be operated in accordance with thepresent invention.

THE PREFERRED EMBODIMENT The refrigeration system shown in the drawingis one which is intended for normal operation in an absorptionrefrigeration cycle and which is particularly well adapted forapplication of the principles of the invention, although it will beobvious that the invention can be applied with facility to otherabsorption refrigeration systems.

Referring to the figure, an upper shell encloses a heatexchanger 12,hereinafter referred to as the condenser coil and forming a portion of acooling circuit 14. Positioned below condenser coil 12 is a receptaclemeans in the form of a pan 16 which cooperates with condenser coil 12and the upper portion of shell 10 to provide a condenser 18.

In the lower portion of shell 10 there is provided a heatexchanger 20,hereinafter referred to as the heating coil, in which flow of a heatingmedium such as steam or hot water is regulated by a valve 22, thedirection of flowbeing indicated by arrows. Valve 22 is connected to acontrol means 22a by a control line 22c. Control means 22a is, in turn,connected in any suitable manner to a temperature-sensitive element 22b.Heating coil forms a portion of a heating circuit which also includespump means as necessary, and a suitable source of heat, neither of whichis shown. The lower portion of shell 10 and the heating coil 20cooperate to provide a generator 24, a generator sump 25 being formed bythe lowermost portion of shell 10. A dashed line 23 represents animaginary plane of demarcation between condenser 18 and generator 24.

A lower shell 26 encloses a heat-exchanger 28, hereinafter referred toas the chilling coil, which forms a portion of a chilling circuitindicated generally at 27 and arranged to circulate chilled fluid to arefrigeration load represented schematically but typically consisting ofone or more air-conditioning units. Also included is a pump 29. Thedirection of flow in chilling circuit 27 is indicated by arrows.Positioned above chilling coil 28 is a refrigerant distribution means inthe form of a spray header 30 having spray nozzles arranged todistribute refrigerant over chilling coil 28 in heat-exchange relationtherewith. Below chilling coil 28 is a receptacle means in the form of apan 32 for collecting liquid refrigerant. Chilling coil 28, spray header30, pan 32, and the upper portion of shell 26 cooperate to provide anevaporator 34.

Below pan 32 there is provided a heat-exchanger 36, hereinafter referredto as the cooling coil, which forms a portion of cooling circuit 14,condenser coil 12 being arranged in series with cooling coil 36. A sprayheader 38 positioned above cooling coil 36 is provided with a number ofspray nozzles. Spray header 38, the lower portion of shell 26 andcooling coil 36 cooperate to provide an absorber 40, the nozzles ofspray header 38 being arranged to distribute an absorbent solution inthe upper portion of absorber 40. A dashed line 41 represents animaginary plane of demarcation between evaporator 34 and absorber 40.

Condenser l8, generator 24, evaporator 34 and absorber 40 are connectedin a closed circuit for conducting the refrigerant and the absorbentsolution in an absorption refrigeration cycle. The closed circuit alsoincludes a concentrated solution passage means 42, a dilute solutionpassage means 44, a condensate line 46, and a refrigerant passage means48. A tube-and-shell heat-exchanger, represented schematically at 50,includes a shell side 52 which forms a portion of concentrated solutionpassage means 42, and a tube side 54 which forms a portion of dilutesolution passage means 44. Concentrated solution passage means 42 alsoincludes a concentrated solution receiver 56 communicating withgenerator 24, and a line 58 connecting concentrated solution receiver 56with shell side 52 of heat-exchanger 50. An eductor 60 is also includedin concentrated solution passage means 42, the eductor having an outlet64 and a suction inlet 62, the latter communicating with shell side 52.A line 66 connecting eductor outlet 64 and spray header 38 completesconcentrated solution passage means 42.

An absorber sump 68 is formed by the lowermost portion of shell 26 andcommunicates with a dilute solution receiver 70 which forms a portion ofdilute solution passage means 44. The latter also includes a solutionpump 72, a line 74 connecting the solution pump inlet and dilutesolution receiver 70, a line 76 connecting the solution pump outlet andtube side 54 of heat-exchanger 50, and a line 77 connecting tube side 54and generator 24. A branch line 78 connects line 76, and thus the outletof solution pump 72, with a motive fluid inlet 79 of eductor 60.

A valve 80 is provided in line 76 for purposes to be explainedhereinafter, valve 80 being normally maintained in a fully open positionto permit unobstructed flow through line 76 during operation of thesystem in an absorption refrigeration cycle.

Condensate line 46 connects pan 16 with evaporator 34 for delivery ofcondensed refrigerant to the evaporator. Refrigerant passage means 48connects pan 32 with spray header 30 and includes a refrigerant receivercommunicating with pan 32, a refrigerant pump 92, a line 94 connectingrefrigerant receiver 90 with the refrigerant pump inlet, and a line 95connecting the refrigerant pump outlet with spray header 30. A blowdownline 96 communicates at one end thereof with line 95 and at the otherend thereof with absorber 40. A blowdown valve 97, which is normallyclosed, is provided to control flow through the blowdown line.

In addition to condenser coil 12 and cooling coil 36, cooling circuit 14includes a line 104 for conducting a cooling medium from cooling coil 36to condenser coil 12, a three-way valve 106, a cooling tower 108, a pump112, a line 114 leading from condenser coil 12 to three-way valve 106, aline 116 leading from three-way valve 106 to cooling tower 108, a line118 leading from cooling tower 108 to pump 112, a line 120 leading frompump 112 to cooling coil 36, and a bypass line 122 leading fromthree-way valve 106 to line 118. Arrows indicate the direction of flowin cooling circuit 14, including condenser coil 12, cooling coil 36 andbypass line 122. Three-way valve 106 is connected to a control means106a by a control line 106c. Control-means 106a is, in turn, connectedby any suitable means to a temperature-sensitive element 106b.

Cooling tower 108 typically includes a housing 124, a spray header 126communicating with line 116 and having a number of spray nozzles, areceptacle means in the form of a coldwater basin 12 8 forming a sump130, a cooling medium receiver 132 communicating with sump 130 and withline 118, and a plurality of fans 134, which may be driven directly, asshown, by electric motors 135, or by intermediate speed reductionmechanisms (not shown). Motors 135 are connected to a control means 135aby a control line 135a. Control means 135a is, in turn, connected by anysuitable means to a temperature-sensitive element l35b. Housing 124 isprovided with a plurality of louvered intake openings 136, a number ofexhaust openings 138, and suitable mounting supports 140 for fans 134and motors 135.

With the exception of valve 80, the structure heretofore described iscommon to a great many existing absorption refrigeration systems. Anynumber of additional features or modifications may be found in suchsystems but do not play any part in the present invention and have beenomitted for the sake of clarity. Among these, for example, are purgedevices for the removal of noncondensible gases from the system, meansfor decrystallizing salts which may precipitate from solution in shellside 52 of heat-exchanger 50 under conditions of relativelyhighconcentration, and a solution valve which may be associated with dilutesolution passage means 44 for reducing the rate of flow of solutiontherein at reduced capacities. On the other hand, a number of featuresshown and described herein are not found in certain existing systems.This is particularly true of eductor 60, which is desirable when asingle solution pump (72) is used. However, the invention is equallyapplicable to systems in which the eductor is omitted or in which asecond solution pump in place of the eductor is provided to circulatesolution to the absorber for distribution therein.

Turning now to the elements added to the conventional structure in thepreferred embodiment of the invention, a receiver 200 is formed by ashell 202 and has an inlet 204 and an outlet 206. A receiver passagemeans in the form of a line 208 connects the receiver inlet 204 with theoutlet of the solution pump 72, or more specifically, with the line 76.The receiver line 208 is provided with a valve 210 for controlling flowtherethrough, valve2l0 being closed during operation of the system in anabsorption refrigeration cycle. As previously mentioned, valve 80 isarranged to permit open flow of solution in concentrated solutionpassage means 44 during normal operation and at other times to preventflow therethrough, for purposes which will be made clear hereinafter. Asecond receiver passage means in the form of a receiver drain line 212connects receiver outlet 206 and absorber 40. Flow from receiver outlet206 is controlled by a valve 214 in drain line 212 which is normallyclosed.

Generator sump 25 and receiver drain line 212 are interconnected by agenerator drain line 216 provided with a valve 218. Valve 218 is closedduring normal operation of the system but may be opened to removeabsorbent solution from generator 24 to absorber 40 for purposes whichare explained below. Generator drain line 216 is shown for convenienceas opening into receiver drain line 212 but may be independentlyconnected to absorber 40. It should be noted that a valve-controlleddrain line interconnecting the generator and the absorber is found insome existing systems.

A refrigerant bypass passage means is indicated generally at 220 andpreferably includes an eductor 222 having a suction inlet 224, an outlet226 and a motive fluid inlet 228. A bypass line 230 connects eductorsuction inlet 224 with line 74 and thus with dilute solution receiver 70and absorber sump 68. Control of flow through bypass line 230 iseffected by a valve 232 which is closed during operation of the systemin an absorption refrigeration cycle. In addition to eductor 222, bypassline 230 and bypass valve 232, bypass passage means 220 includes amotive fluid line 234 connecting motive fluid inlet 228 with line 95 andthus with the outlet of refrigerant pump 92. Flow in motive fluid line234 is controlled by a valve 236 which is normally closed. Bypasspassage means 220 also includes a line 238 connecting eductor outlet 226with the inlet of refrigerant pump 92.

A pump coolant line 240 connects line 94 with an internal coolantcircuit (not shown) of refrigerant pump 92. Flow in coolant line 240 iscontrolled by a valve 242 which is closed during operation of the systemin an absorption refrigeration cycle.

For purposes of this description it will be assumed that water is usedas the refrigerant, as the cooling medium incooling circuit 14, and asthe fluid to be chilled in chilling coil'28 for circulation to therefrigeration load; that the heating medium circulated in heating coil20 is steam; and that the absorbent solution is an aqueous solution oflithium bromide which may also contain suitable additives for improvedheat transfer performance and the inhibition of corrosion. As previouslynoted, other fluids may be employed, and the invention is in no wayrestricted to the use of the foregoing substances.

NORMAL OPERATION Normal operation; that is, operation of the system inan absorption refrigeration cycle, will now be described. It will beunderstood that the expressions normal and normally" as used hereinrefer to, such operation. v

The pressure in lower shell 26 is maintained at a value (for example,about 7 mm. Hg absolute of l/ 100 atmosphere) substantially lower thanthe pressure in upper shell 10 (for example, about 75 mm. Hg absolute orl/lO atmosphere). The force of gravity and the pressure differentialinduce flow of condensed refrigerant from condenser pan 16 throughcondensate line 46 to the upper portion of evaporator 34 where afraction of the condensed refrigerant flashes into vapor. As condensateentering the evaporator is vaporized, heat is abstracted from the watercirculating in chilling coil 28, unvaporized refrigerant being collectedin evaporator pan 32 from which it is conducted by way of refrigerantreceiver 90, line 94, refrigerant pump 92 and line 95 to spray header30, valve 236 being closed during this phase of operation. The liquidrefrigerant is distributed by spray header 30 over chilling coil 28 forfurther vaporization and consequent abstraction of additional heat fromthe water to be chilled. Any unvaporized refrigerant will continue to becollected by pan 32 for recirculation to spray header 30.

The refrigerant vaporized in evaporator 34 passes to absorber 40, owingto a slight pressure differential within shell 26 which arises from theabsorption process and the effect of the sprays issuing from the nozzlesof spray header 38. The vaporized refrigerant comes into contact withand is absorbed by the solution issuing from the spray header. Thesolution is thereby diluted as it falls to absorber sump 68, the heat ofsolution being abstracted by the cooling water circulated in coolingcoil 36.

The dilute absorbent solution is removed from absorber sump 68 by way ofdilute solution receiver 70 and line 74, solution pump 72 acting toforward the dilute solution to generator 24 through line 76, tube side54 of heat-exchanger.

50, and line 77. Valve is fully open and valve 232 closed during thisphase of operation.

The dilute solution is heated in generator 24 by the steam circulatingin heating coil 20, whereby refrigerant is evaporated from the solution.The evaporated refrigerant rises to condenser 18 where it is liquefiedby the rejection of the heat of evaporation to the cooling watercirculating in condenser coil 12, the liquid refrigerant being collectedin pan 16 to complete the refrigerant cycle.

The evaporation of refrigerant from the absorbent solution in generator24 increases the concentration of the solution, and theconcentratedsolution spills from generator sump 25 into concentrated solutionreceiver 56, valve 218 being closed during this phase of operation. Theconcentrated solution flows from receiver 56 through line 58 to shellside 52 of heatexchanger 50, where it rejects heat to the dilutesolution flowing through tube side 54. This exchange of heat enhancesthe efficiency of the system by cooling the concentrated solution toincrease its capacity for absorption and by preheating the dilutesolution on its way to generator 24. From shell side 52 the concentratedsolution is drawn to suction inlet 62 of eductor 60. A portion of theflow of dilute solution from the outlet of solution pump 72 is divertedthroughbranch line 78 to motive fluid inlet 79 of eductor 60 to providea motive force for operation of the eductor. Consequently theconcentrated solution entering suction inlet 62 and the dilute solutionentering motive fluid inlet 79 are mixed in the eductor to provide asolution of intermediate concentration at outlet 64, the eductor actingto forward the intermediate solution through line 66 to spray header 38for distribution in the upper portion of absorber 40, thus completingthe absorbent solution cycle. As previously pointed out, eductor 60 maybe omitted from some systems. In the absence of eductor 60, the force ofgravity and the pressure differential between shells 10 and 26 may berelied upon to conduct the concentrated solution from generator 24 toabsorber spray header 38. Alternatively, a second solution pump may beprovided in place of eductor 60, as mentioned above. The second solutionpump may be arranged to circulate solution of intermediate concentrationto the spray header in the absorber as shown and described in, forexample, US. Pat. No. 3,254,499, issued June 7, 1966 to N. E. Hopkins.

The water chilled in chilling coil 28 is circulated to the refrigerationload and returned to the chilling coil by the action of pump 29.

Capacity control is exercised by employing valve 22 to regulate the flowof steam through heating coil 20. Also, as previously mentioned, asolution control valve (not shown) may be associated with dilutesolution passage means 44.

The position of valve 22 is normally controlled by control means 220acting through control line 22c. Control means 22a is typically athermostat device responsive to temperature-sensitive element 22b, thelatter element being arranged to sense the temperature of the chilledwater leaving chilling coil 28. In the typical system, the refrigerationload might call for a leaving chilled water temperature of 44 F. at fullload. If control means 22a is a simple proportional control, a low-loadcondition might call for a controlled leaving chilled water temperatureof 41 F., in which case the valve 22 would be in a throttling position.While this type of control has the advantages of simplicity and economy,it does not take into account the fact that at light load conditions thechilled water can be supplied at a somewhat higher temperature to therefrigeration load. In the alternative refrigeration cycle to bedescribed below, advantage is taken of the fact that at the lighter loadconditions the chilled water can be supplied to the load at temperaturessomewhat above the full load design temperature.

Turning now to the operation of cooling circuit 14, the cooling waterenters cooling coil 36 from line 120 and thus from the outlet of pump112. After it has circulated in cooling coil 36 to abstract heat fromthe absorbent solution in absorber 40, the cooling water is led throughline 104 to condenser coil 12 where it is circulated to liquefy theevaporated refrigerant by abstracting the heat of evaporation. Underdesign operating conditions; that is, with a heavy refrigeration loadand high ambient temperatures, three-way valve 106 is positioned topermit open communication between lines 1 14 and 116 and to block flowthrough bypass line 122. Under such conditions the cooling water isconducted from the condenser coil 12 through line 114, valve 106 andline 116 to spray header 126 from which it issues downwardly in a seriesof sprays. Fans 134 are operated to draw the ambient air inwardlythrough louvered openings 136, upwardly through the cooling watersprays, and outwardly through exhaust openings 138, the air abstractingheat from the cooling water in its passage through the sprays, primarilyby partial evaporation. The water thus cooled falls to sump 130 formedby cold water basin 138 and is conducted therefrom. to the inlet of pump112 by way of receiver 132 and line 118 to complete the cooling watercycle. For the reasons discussed earlier in this specification, thetemperature of the cooling water entering cooling coil 36 isconventionally maintained at a relatively high value, the designtemperature typically being between 75 F. and 90 F. Further, it has beenconsidered desirable for stable operation to maintain the enteringtemperature within 292 of the design temperature; that is, within atotal range of 5. This is accomplished by controlling the position ofthree-way valve 106 using control means 106a which acts through controlline 106c. Control means 106a is typically a thermostat deviceresponsive to temperature-sensitive clement 106b, the latter elementbeing arranged to sense the temperature of the cooling water enteringcooling coil 36. Further control of the cooling water temperature iseffected by operating fan motors 135, either by varying their speed orexercizing on-off control. This is done by control means 135a actingthrough control line 1350. Control means 135a is typically a thermostatdevice responsive to temperature-sensitive element 135b, the latterelement being arranged to sense the temperature of the cooling waterleaving the cooling tower 108. For example, if the design temperature ofthe cooling water entering cooling coil 36 is 85 F., control means 135amight be set to energize fan motors 135 if the temperature attemperature-sensitive element 135a should rise to F., and to deenergizethe fan motors if the temperature should fall to 75 F. Three-way valve106 acts to control the temperature of the cooling water by causing allor a portion of the flow, as necessary, to be bypassed around coolingtower 108 through bypass line 122. It should be pointed out that bypassline 122 is preferably located indoors in a heated space in order toavoid delivery of a slug of relatively cold water to cooling coil 36 andcondenser coil 12 upon commencement of operation of the system. It willalso be recognized that a bypass line such as line 122 may be equallyuseful when a body of water of variable temperature is employed in placeof cooling tower 108.

For purposes of this description, normal operation of the system in theabsorption refrigeration cycle, as heretofore described, will bereferred to as phase A. During phase A valve 22 is open or partiallyopen depending on the magnitude of the refrigeration load, valve 80 isfully open, valve 214 may be open, and valves 97, 210, 218, 232, 236 and242 are closed. Chilled-water pump 29, solution pump 72, refrigerantpump 92 and cooling-water pump 112 are, of course, operative duringphase A.

OPERATION IN ALTERNATIVE REFRIGERATION CYCLE Now, by way of example,assuming that the design temperature of the cooling water enteringcooling coil 36 is F that the actual temperature has been maintainedbetween 825 F. and 875 F. but that the temperature of the air out ofdoors has become sufficiently low that cooling water could be providedat a temperature of 44 F. or lower by making appropriate use of coolingtower 108; and that the present refrigeration load would be satisfied bychilled water leaving chilling coil 28 at a temperature of 50 F., theabsorption refrigeration cycle can be discontinued and an alternativerefrigeration cycle commenced in accordance with the present invention.In a typical system, a 6 difference between the chilled water andcooling water temperatures would permit operation in the alternativerefrigeration cycle at 49.5 percent of design full load capacity in theabsorption refrigeration cycle. The fraction of full load capacity is afunction of the temperature difference whereby, in the same typicalsystem, a 4 difference would permit 32 percent of full load capacity,and an 8 difference 67.5 percent.

To proceed from operation in an absorption refrigeration cycle tooperation in the alternative refrigeration cycle, hereinafter called thefree cooling cycle, or simply free cooling, the system is first shutdown temporarily and absorbent solution is removed from the absorber,this phase being referred to hereinafter as phase B. More particularly,control means 22a is overridden by any suitable means to close valve 22,halting the circulation of steam in heating coil 20 and therebydiscontinuing the supply of heat to generator 24 and rendering generator24 and condenser 18 inoperative. Operation of pump 112 is discontinuedto halt circulation in coolingwater circuit 14. Pumps 29 and 92 mayremain in operation.

At the commencement of phase B, valve 218 is opened to drainconcentrated solution from generator 24 to absorber 40. This willprevent refrigerant vapor from being absorbed in the generator duringoperation in the free cooling cycle, thereby avoiding loss ofrefrigerant from the cycle and possible increase of solution ingenerator 24 to a level at which it might overflow into absorber 40 byway of concentrated solution passage means 42. At the same time, valves80 and 214 are closed and valve 210 opened so that solution pump 72,which remains in operation, will now forward absorbent solution fromabsorber sump 68 to receiver 200 by way of line 208 and receiver inlet204. Valves 97, 232, 236 and 242 remain closed during phase B.

In a typical system it will take approximately to minutes to transferthe absorbent solution from absorber 40 to receiver 200. This includesthe solution which is drained from generator 24 to the absorber. Itshould be pointed out that receiver 200 and the associated lines (208,212) and valves (80, 210, 214) are not essential, since the removal ofabsorbent solution from the system can be accomplished by discontinuingoperation of solution pump 72 and draining absorbent solution from theabsorber by any suitable means for storage in drums or other containers.A service drain (not shown) usually provided on solution pump 72 can beused for this purpose. Alternatively, the absorbent solution can bestored in the upper shell 10 by providing appropriate isolation valves.lf receiver 200 is provided, however, it can also be used for otherpurposes since it permits convenient removal and storage of refrigerant,absorbent solution, or a mixture of both. This might be done, by way ofexample, for convenience in servicing a component of the system.

When the absorbent solution has been removed from absorber 40, operationof solution pump 72 is discontinued and valve 210 is closed to terminatephase B. A small amount of absorbent solution will remain in solutionreceiver 70, line 74 and solution pump 72. This residual solution willhave little effect during operation in the free cooling cycle, asexplained hereinafter, but can be removed if desired by way of thepreviously mentioned service drain on solution pump 72. Alternatively, asmall service transfer pump (not shown) may be provided to transfer theresidual solution to receiver 200.

Operation in the free cooling cycle may now be commenced, this phase ofoperation being referred to hereinafter as phase C. Refrigerant pump 92remaining in operation, refrigerant is forwarded from pan 32 to sprayheader 30 with consequent vaporization of the refrigerant andabstraction of heat from the water circulated in chilling coil 28.Control means 106a is overridden by any suitable means to adjustthree-way valve 106 to a position permitting full circulation of thecooling water to cooling tower 108, operation of pump 112 is resumed,and control of fan motors 135 is effected to provide the lowest possiblecooling water temperature to a lower limit of a few degrees abovefreezing. For example, if the fan motors are started and stopped as themeans of controlling fan capacity, control means 135a might be reset toenergize the fan motors 135 if the temperature of the cooling waterleaving the cooling tower 108 should rise to 40 F., and deenergize thefan motors if the temperature should fall to 26 F.

Absorber 40 will now act as a condenser, the vaporized refrigerantpassing from evaporator 34 to absorber 40 to be reduced to condensate asit rejects the heat of vaporization to the cooling water circulated incooling coil 36, the condensate falling to absorber sump 68. Thereduction of vaporized refrigerant to condensate results in a pressuredifferential within shell 26 sufficient to draw vapor from evaporator 34to absorber 40.

Valve 236 is opened to supply motive fluid to eductor 222, and valve 242is opened to supply refrigerant to the coolant circuit (not shown) ofrefrigerant pump 92 in consideration of the additional load placed onthe pump during operation in the free cooling cycle. Simultaneously,valve 232 is opened whereby eductor 222 withdraws condensed refrigerantfrom absorber sump 68 by way of solution receiver 70 and line 230, andforwards it to the suction side of refrigerant pump 72 by way of line238.

The system can continue to be operated in phase C, that is, in the freecooling cycle, so long as it is possible to maintain the temperature ofthe cooling water entering cooling coil 36 at a value below atemperature of the chilled water which will satisfy the refrigerationload. This may be a matter of a number of hours in the event of anunseasonable and temporary lowering of the temperature of the ambientair, or it may amount to several months during the winter season incertain climates. During phase C valves 80, 97, 210 and 214 remainclosed, valve 218 may also remain closed, and solution pump 72 remainsinoperative. Most importantly, the major source of energy put into thesystem during operation in an absorption refrigeration cycle, namely thesupply of heat to generator 24, is omitted during operation in the freecooling cycle by maintaining valve 22 closed, it being necessary to putenergy into the system only at pumps 29 and 112 and refrigerant pump 92'Energy is also supplied to fan motors 135, but this may be intermittentsince it is not required when the temperature of the ambient air is lowenough to provide cooling water at a sufficiently low temperaturewithout operation of fans 134.

If the residual solution is not removed from solution receiver 70, line74 and solution pump 72, it will eventually form a mixture with therefrigerant, resulting in a solution concentration of approximately 5percent by weight in a typical system. This amount of salt will resultinonly a small reduction in capacity and can easily be tolerated. Forexample, under the conditions described, the capacity might be reducedfrom the previously mentioned 49.5 percent of design full load capacityto 44.5 percent. Alternatively, a small still may be used to remove saltfrom the refrigerant to eliminate this small reduction in capacity. Sucha still may be arranged to divert a small stream of refrigerant from thedischarge of refrigerant pump 92 to a small boiler heated by electrical,steam or other heating means. The water driven off as vapor in theboiler would be directed to absorber 40 to be condensed on cooling coil26. The solution remaining would be concentrated to approximately 55percent concentration and directed to receiver 200 or heat-exchanger 50for storage.

Now, if the temperature of the air out of doors should rise to a valueat which it is not longer possible to provide cooling water at asufficiently low temperature, operation in the free cooling cycle isdiscontinued and absorber 40 is again charged with absorbent solution,this phase of operation being referred to hereinafter as phase D. Tocommence phase D, valves 232 and 236 are closed, thereby ceasingoperation of eductor 222 and halting the withdrawal of refrigerant fromabsorber sump 68. Operation of pumps 29, 92 and 112 is discontinued, andvalve 242 is closed to halt delivery of refrigerant through line 240 tothe coolant circuit of refrigerant pump 92. Pump 72 remains inoperative.

Valve 218 remains closed to prevent any further draining of solutionfrom generator 24 to absorber 40. Next, valve 214 is opened to transferthe absorbent solution from receiver 200 to absorber 40 by way of line212. Valves and 210 remain closed during phase D.

When all the absorbent solution has been transferred from receiver 200,operation of the system in an absorption refrigeration cycle is resumed,this phase being referred'to hereinafter as phase B, by opening valve 22to resume the 1 supply of heat to the generator, opening valve 80, andresuming operation of pumps 29, 72, 92 and 112. The position ofthree-way valve 106 is adjusted and control means 135a is reset asnecessary to supply cooling water to cooling coil 36 at a temperaturewithin the design range.

During phase E, all valves are positioned as in phase A except thatblowdown valve 97 is opened slightly to divert a portion of the flow ofrefrigerant from line 95 to absorber 40 by way of blowdown line 96. Thishas the effect of speeding the separation of the small proportion ofresidual solution present in the refrigerant during operation in thefree cooling cycle. If there is considerable excess capacity available,as there would normally be at the end of a cool season and the beginningof a warm season, the refrigerant can be purified in this manner at arelatively rapid rate. In a typical system, blowdown valve 97 can beclosed in approximately one-half hour, whereby the system is returned tophase A; that is, fully normal operation I in an absorptionrefrigeration cycle.

If the residual solution was removed from solution receiver 70, line 74and solution pump 72 before initiation of the free cooling cycle, thereis no need to open blowdown valve 97 at all, and phase E is thusomitted, the system being returned to phase A following or during phaseD.

The various operating phases are summarized in table 1 hereof and thevalve settings and pump operative conditions are given for each phase intable [1 hereof.

TABLE 1 Phase A: Fully normal operation in absorption refrigerationcycle.

Phase B: Termination of absorption refrigeration cycle;

removal of absorbent solution.

Phase C: Operation in alternative refrigeration cycle (free coolingcycle).

Phase D: Termination of alternative refrigeration cycle (free coolingcycle); return of absorbent solution.

Phase E: Resumption of operation in absorption refrigeration cycle withblowdown of refrigerant in preparation for return to phase A.

TABLE II It will be noted that little modification of conventional orexisting systems is required to practice the invention. As previouslypointed out, a generator drain line such as the line 216 and anassociated valve are already provided in some existing systems. It hasalso been pointed out that receiver 200 and the valves and linesassociated therewith are not essential. Depending on the characteristicsof the particular refrigerant pump employed, eductor 222, valves 236 and242 and associated lines can also be omitted. Accordingly, manyconventional or existing systems can be modified for operation inaccordance with the present invention simply by adding a valvecontrolledbypass line communicating at one end thereof with the absorber sump andat the other end thereof with the evaporator.

The various valves and pumps shown and described herein. includingthree-way valve 106, can be actuated manually in carrying out the methodof the invention or they can be constructed and arranged for remoteactuation, for example from a central control station, by employing anyof a number of well-known mechanical, electrical, hydraulic andpneumatic devices. In addition, fully automatic operation of any or allof the valves and pumps can be effected by making appropriate use of anyof several equally well known devices which are sensitive totemperature, pressure, rate of flow, fluid density, electricalconductivity or the like.

It should also be pointed out that free cooling should not be initiatedif the degree of concentration of the absorbent solution is so greatthat crystallization might occur in receiver 200 or concentratedsolution passage means 42 under expected conditions of temperature inthe spaces in which they are located. Similarly, the degree ofconcentration should not be so low that an insufficient amount ofrefrigerant will be available for operation in the free cooling cycle,whereby refrigerant pump 92 might be subject to cavitation. When thesystem has been operating for some time in the absorption refrigerationcycle, the level of concentration will normally be within the rangewhich satisfies these two requirements. However, wellknown controls canbe provided to prevent the commencement of phase B if the concentrationlevel is outside the Operative.

Do. Do.

The procedure to be followed in converting the system from operation inan absorption refrigeration cycle to the free cooling cycle and viceversa has been divided into distinct phases for purposes ofillustration. In actual practice the transition between phases iscarried out in a smooth, continuous sequence as the correspondingconditions arise.

On the other hand, in describing the sequence of phases it has beenassumed that refrigeration requirements call for virtually continuousoperation of the system. It is entirely possible in many installationsthat the requirement for refrigeration may be intermittent or onlyoccasional during periods in which conditions permit the system to beoperated in the free cooling cycle. If the system is inoperative and arequirement for refrigeration arises when the conditions for freecooling are present, the system is placed in condition for operation inphase A and briefly operated in that phase before proceeding to phases Band C.

desirable range. Controls can also be provided which will initiate amixing phase to reduce the concentration before phase B is commenced or,if concentration is too low, to continue operation in phase A until anacceptable level of concentration is achieved.

Also, if for any reason the concentration of salts in the refrigerantshould rise to an unacceptable level during operation in the freecooling cycle, operation of the system can be returned temporarily tophase E (by way of phase D) until the concentration has been reducedsatisfactorily. Free cooling can then be resumed by proceeding to phaseB and then to phase C.

While the invention has been described in connection with a specificembodiment thereof, it is to be understood that this is by way ofillustration and not by way of limitation; and the scope of the appendedclaims should be construed as broadly as the prior art will permit.

We claim:

1. In a method of operating a refrigeration system of the type haying anevaporator and an absorber connected in a closed circuit for normallyconducting a refrigerant and an absorbent solution in an absorptionrefrigeration cycle, the absorber being arranged in the closed circuitto receive refrigerant vaporized in the evaporator and normally beingprovided with absorbent solution for absorption of the vaporizedrefrigerant; means defining a chilling circuit for circulating a chilledfluid in heat-exchange relation with a refrigeration load and includinga first heat-exchanger in the evaporator for abstracting heat from thefluid and rejecting it to the refrigerant to chill the fluid and tovaporize the refrigerant; and means defining a cooling circuit forcirculating a cooling medium and including a second heat-exchanger inthe absorber for normally abstracting heat from the absorbent solutionand rejecting it to the cooling medium; the steps of operating theabsorber to condense the vaporized refrigerant, in the absence ofabsorbent solution in the absorber, by circulating the cooling medium inthe second heatexchanger at a temperature lower than a temperature ofthe chilled fluid which will satisfy the refrigeration load; andcirculating refrigerant condensed in the absorber to the evaporator.

2. in a method of operating a refrigeration system of the type having anevaporator and an absorber connected in a closed circuit for normallyconducting a refrigerant and an absorbent solution in an absorptionrefrigeration cycle, the absorber being arranged in the closed circuitto receive refrigerant vaporized in the evaporator and normally beingprovided with absorbent solution for absorption of the vaporizedrefrigerant; means defining a chilling circuit for circulating a chilledfluid in heat-exchange relation with a refrigeration load and includinga first heat-exchanger in the evaporator for abstracting heat from thefluid and rejecting it to the refrigerant to chill the fluid and tovaporize the refrigerant; and means defining a cooling circuit forcirculating a cooling medium and including a second heat-exchanger inthe absorber for normally abstracting heat from the absorbent solutionand rejecting it to the cooling medium; the steps of removing absorbentsolution from the absorber; operating the absorber to condense thevaporized refrigerant by circulating the cooling medium in the secondheat-exchanger at a temperature lower than a temperature of the chilledfluid which will satisfy the refrigeration load; and conductingrefrigerant condensed in the absorber to the evaporator.

3. in a method of operating a refrigeration system of the type having anevaporator, an absorber, a generator and a condenser connected in aclosed circuit for normally conducting a refrigerant and an absorbentsolution in an absorption refrigeration cycle, the absorber beingarranged in the closed circuit to receive refrigerant vaporized in theevaporator, the generator normally being operative to supply absorbentsolution to the absorber for absorption of the vaporized refrigerant,the condenser normally being operative to supply condensed refrigerantto the evaporator; means defining a chilling circuit for circulating achilled fluid in heat-exchange relation with a refrigeration load andincluding a first heatexchanger in the evaporator for abstracting heatfrom the fluid and rejecting it to the refrigerant to chill the fluidand to vaporize the refrigerant; and means defining a cooling circuitfor circulating a cooling medium and including a second heatexchanger inthe absorber for normally abstracting heatfrom the absorbent solutionand rejecting it to the cooling medium; the steps of removing absorbentsolution from the absorber; operating the absorber to condense thevaporized refrigerant by circulating the cooling medium in the secondheatexchanger at a temperature lower than a temperature of the chilledfluid which will satisfy the refrigeration load; and circulatingrefrigerant condensed in the absorber to the evaporator; said stepsbeing carried out with the generator and the condenser inoperative.

4. The method according to claim 3. including the steps of discontinuingcirculation of the condensed refrigerant from the absorber to theevaporator; charging the absorber with absorbent solution; commencingoperation of the generator and the condenser; and circulating thecooling medium in the second heat-exchanger at a temperature higher thansaid temperature of the chilled fluid.

5. In a method of operating a refrigeration system of the type having anevaporator, an absorber, a generator and a condenser connected in aclosed circuit normally conducting a refrigerant and an absorbentsolution in an absorption refrigeration cycle, the absorber beingarranged in the closed circuit to receive refrigerant vaporized in theevaporator, the generator normally being operative to supply absorbentsolution to the absorber 'for absorption of the vaporized refrigerant,the condenser normally being operative to supply condensed refrigerantto the evaporator; means defining a chilling circuit circulating achilled fluid in heat-exchange relation with a refrigeration load andincluding a first heatexchanger in the evaporator for abstracting heatfrom the fluid and rejecting it to the refrigerant to chill the fluidand to vaporize the refrigerant, the temperature of the chilled fluidleaving the first heat-exchanger normally being maintained within afirst range of values; means defining a cooling circuit circulating acooling medium and including a second heatexchanger in the absorber fornormally abstracting heat from the absorbent solution and rejecting itto the cooling medium, the temperature of the cooling medium enteringthe second heat-exchanger normally being maintained within a secondrange of values having an upper limit higher than the upper limit of thefirst range; the steps of removing absorbent solution from the absorber;operating the absorber to condense the vaporized refrigerant byadjusting the temperature of the cooling medium entering the secondheat-exchanger to a value lower than the temperature of the chilledfluid leaving the first heat-exchanger; and conducting refrigerantcondensed in the absorber to the evaporator; said steps being carriedout with the generator and the condenser inoperative.

6. The method according to claim 5, including the steps of discontinuingcirculation of the condensed refrigerant from the absorber to theevaporator; charging the absorber with absorbent solution, commencingoperation of the generator and the condenser; and adjusting thetemperature of the cooling medium entering the second heat-exchanger toa value within the second range and higher than the temperature of thechilled fluid leaving the first heat-exchanger.

7. In a method of operating a refrigeration system of the type having anevaporator, an absorber, a generator, and a condenser connected in aclosed circuit normally conducting a refrigerant and an absorbentsolution in an absorption refrigeration cycle, the absorber beingarranged in the closed circuit to receive refrigerant vaporized'in theevaporator and normally to receive absorbent solution from the generatorfor absorption of the vaporized refrigerant; means defining a chillingcircuit circulating a chilled fluid in heat-exchange relation with arefrigeration load and including a first heatexchanger in the evaporatorfor abstracting heat from the fluid and rejecting it to the refrigerantto chill the fluid and to vaporize the refrigerant, the temperature ofthe chilled fluid leaving the first heat-exchanger normally beingmaintained within a first range of values; means defining a coolingcircuit circulating a cooling medium and including a secondheatexchanger in the absorber for normally abstracting heat from theabsorbent solution and rejecting it to the cooling medium, thetemperature of the cooling medium entering the second heat-exchangernormally being maintained within a second range of values having anupper limit higher than the upper limit of the first range; and meansdefining a heating circuit normally conducting flow of a heating mediumand including a third heat-exchanger in the generator for normallyabstracting heat from the heating medium and rejecting it to theabsorbent solution; the steps of discontinuing operation of thegenerator and the condenser, and thereby interrupting the absorptionrefrigeration cycle, by discontinuing flow of the heating medium in thethird heat-exchanger; removing absorbent solution from'the absorber andthe generator; operating the absorber to condense the vaporizedrefrigerant by adjusting the temperature of the cooling medium enteringthe second heat-exchanger to a value lower than the temperature of thechilled fluid leaving the first heat-exchanger; and circulatingrefrigerant condensed in the absorber to the evaporator.

8. The method according to claim 7, including the steps of discontinuingcirculation of the condensed refrigerant from the absorber to theevaporator; returning the absorbent solution to the absorber and thegenerator; resuming operation of the generator and the condenser byresuming flow of the heating medium in the third heat-exchanger; andadjusting the temperature of the cooling medium entering the secondheatexchanger to a value within the second range and higher than thetemperature of the chilled fluid leaving the first heatexchanger.

9. In a refrigeration system including an evaporator and an absorberconnected in a closed circuit for normally conducting a refrigerantandan absorbent solution in an absorption refrigeration cycle, the absorberbeing arranged in the closed circuit to receive refrigerant vaporized inthe evaporator and normally being provided with absorbent solution forabsorption of the vaporized refrigerant; means defining a chillingcircuit for circulating a chilled fluid in heat-exchange relation with arefrigeration load and including a first heat-exchanger in theevaporator for abstracting heat from the fluid and rejecting it to therefrigerant to chill the fluid and to vaporize the refrigerant; andmeans defining a cooling circuit for circulating a cooling medium andincluding a second heat-exchanger in the absorber for normallyabstracting heat from the absorbent solution and rejecting it to thecooling medium; means for operating the absorber to condense thevaporized refrigerant, in the absence of absorbent solution in theabsorber, when the temperature of the cooling medium entering the secondheat-exchanger is lower than a temperature of the chilled fluid whichwill satisfy the refrigeration load, the lastmentioned means includingbypass passage means communicating at one end thereof with the absorberand at the other end thereof with the evaporator, and bypass valve meansassociated with the bypass passage means for controlling flow therein,the bypass valve means having a normally closed position and beingmovable to an open position for the circulation of refrigerant condensedin the absorber to the evaporator.

10. The combination according to claim 9, including refrigerantdistribution-means in the evaporator for distributing unvaporizedrefrigerant over the first heat-exchanger;

receptacle means in the evaporator below the first heatexchanger forcollecting unvaporized refrigerant; and refrigerant passage meansconnecting the distribution means and the receptacle means forconducting unvaporized refrigerant from the receptacle means to thedistribution means; said other end of the bypass passage meanscommunicating with the refrigerant passage means for circulation ofcondensed refrigerant from the absorber to the distribution means whenthe bypass valve means is in its open position.

11. The combination according to claim 10, wherein the refrigerantpassage means includes a refrigerant pump having an inlet incommunication with the receptacle means and an outlet in communicationwith the distribution means, the bypass passage means connecting theabsorber and the refrigerant pump inlet.

12. The combination according to claim 11. wherein the bypass passagemeans includes an eductor having an outlet. a suction inlet, and amotive fluid inlet, the eductor outlet communicating with the pumpinlet,the eductor suction inlet communicating with the absorber; motive fluidpassage means connecting the pump outlet and the motive fluid inlet; andmotive fluid valve means being associated with the motive fluid passagemeans for controlling flow therein; the motive fluid valve means havinga normally closed position and being movable to an open position foroperating the eductor to withdraw condensed refrigerant from theabsorber when the bypass valve means is in its open position.

13. The combination according to claim 9, including means for removingabsorbent solution from the absorber and com prising receiver means forstoring the absorbent solution, said receiver means having an inlet,receiver passage means communicating at one end thereof with thereceiver inlet, a solution pump having an inlet communicating with theabsorber and having an outlet communicating with the other end of thereceiver passage means, and receiver valve means associated with thereceiver passage means for controlling flow therein, the receiver valvemeans having a normally closed position and being movable to an openposition for removal of the absorbent solution from the absorber to thereceiver means.

14. The combination according to claim 13, wherein said receiver meanshas an outlet, second receiver passage means communicating at one endthereof with the receiver outlet and at the other end thereof with theabsorber, second receiver valve means being associated with the secondreceiver passage means for controlling flow therein, the second receivervalve means having a normally closed position and being movable to anopen position for removal of absorbent solution from the receiver meansto the absorber.

- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3:108 Dated February 8, 1972 Inventor(5) E. HOpkinB et 3-1 It is certifiedthat error appears in the above-identified patent and that said LettersPatentare hereby corrected as shown below:

Column 1, line 41, "abstraction". should read abstracting Column 6, line34, "of 1 100" should Colman 9, line 71,- "2 should read read or 1/100.36

Signed and sealed this 24th day of October 1972.

(SEAL) Atteat:

EDWARD M.FLETCHER,JR. I ROBERT GOT'I'SCHALK Atteeting OfficerCommissioner of Patent USCOMM-DC 60376-1 69 Q UvS. GOVERNMENT PRINTINGOFFICE: 1959 0-366-334.

FORM PO-1OSO (10-69)

1. In a method of operating a refrigeration system of the type having anevaporator and an absorber connected in a closed circuit for normallyconducting a refrigerant and an absorbent solution in an absorptionrefrigeration cycle, the absorber being arranged in the closed circuitto receive refrigerant vaporized in the evaporator and normally beingprovided with absorbent solution for absorption of the vaporizedrefrigerant; means defining a chilling circuit for circulating a chilledfluid in heat-exchange relation with a refrigeration load and includinga first heat-exchanger in the evaporator for abstracting heat from thefluid and rejecting it to the refrigerant to chill the fluid and tovaporize the refrigerant; and means defining a cooling circuit forcirculating a cooling medium and including a second heat-exchanger inthe absorber for normally abstracting heat from the absorbent solutionand rejecting it to the cooling medium; the steps of operating theabsorber to condense the vaporized refrigerant, in the absence ofabsorbent solution in the absorber, by circulating the cooling medium inthe second heatexchanger at a temperature lower than a temperature ofthe chilled fluid which will satisfy the refrigeration load; andcirculating refrigerant condensed in the absorber to the evaporator. 2.In a method of operating a refrigeration system of the type having anevaporator and an absorber connected in a closed circuit for normallyconducting a refrigerant and an absorbent solution in an absorptionrefrigeration cycle, the absorber being arranged in the closed circuitto receive refrigerant vaporized in the evaporator and normally beingprovided with absorbent solution for absorption of the vaporizedrefrigerant; means defining a chilling circuit for circulating a chilledfluid in heat-exchange relation with a refrigeration load and includinga first heat-exchanger in the evaporator for abstracting heat from thefluid and rejecting it to the refrigerant to chill the fluid and tovaporize the refrigerant; and means defining a cooling circuit forcirculating a cooling medium and including a second heat-exchanger inthe absorber for normally abstracting heat from the absorbent solutionand rejecting it to the cooling medium; the steps of removing absorbentsolution from the absorber; operating the absorber to condense thevaporized refrigerant by circulating the cooling medium in the secondheat-exchanger at a temperature lower than a temperature of the chilledfluid which will satisfy the refrigeration load; and conductingrefrigerant condensed in the absorber to the evaporator.
 3. In a methodof operating a refrigeration system of the type having an evaporator, anabsorber, a generator and a condenser connected in a closed circuit fornormally conducting a refrigerant and an absorbent solution in anabsorption refrigeration cycle, the absorber being arranged in theclosed circuit to receive refrigerant vaporized in the evaporator, thegenerator normally being operative to supply absorbent solution to theabsorber for absorption of the vaporized refrigerant, the condensernormally being operative to supply condensed refrigerant to theevaporator; means defining a chilling circuit for circulating a chilledfluid in heat-exchange relation with a refrigeration load and includinga first heat-exchanger in the evaporator for abstracting heat from thefluid and rejecting it to the refrigerant to chill the fluid and tovaporize the refrigerant; and means defining a cooling circuit forcirculating a cooling medium and including a second heat-exchanger inthe absorber for normally abstracting heat from the absorbent solutionand rejecting it to the cooling medium; the steps of removing absorbentsolution from the absorber; operating the absorber to condense thevaporized refrigerant by circulating the cooling medium in the secondheat-exchanger at a temperature lower than a temperature of the chilledfluid which will satisfy the refrigeration load; and circulatingrefrigerant condensed in the absorber to the evaporator; said stepsbeing carried out with the generator and the condenser inoperative. 4.The method according to claim 3, including the steps of discontinuingcirculation of the condensed refrigerant from the absorber to theevaporator; charging the absorber with absorbent solution; commencingoperation of the generator and the condenser; and circulating thecooling medium in the second heat-exchanger at a temperature higher thansaid temperature of the chilled fluid.
 5. In a method of operating arefrigeration system of the type having an evaporator, an absorber, agenerator and a condenser connected in a closed circuit normallyconducting a refrigerant and an absorbent solution in an absorptionrefrigeration cycle, the absorber being arranged in the closed circuitto receive refrigerant vaporized in the evaporator, the generatornormally being operative to supply absorbent solution to the absorberfor absorption of the vaporized refrigerant, the condenser normallybeing operative to supply condensed refrigerant to the evaporator; meansdefining a chilling circuit circulating a chilled fluid in heat-exchangerelation with a refrigeration load and including a first heat-exchangerin the evaporator for abstracting heat from the fluid and rejecting itto the refrigerant to chill the fluid and to vaporize the refrigerant,the temperature of the chilled fluid leaving the first heat-exchangernormally being maintained within a first range of values; means defininga cooling circuit circulating a cooling medium and including a secondheat-exchanger in the absorber for normally abstracting heat from theabsorbent solution and rejecting it to the cooling medium, thetemperature of the cooling medium entering the second heat-exchangernormally being maintained within a second range of values having anupper limit higher than the upper limit of the first range; The steps ofremoving absorbent solution from the absorber; operating the absorber tocondense the vaporized refrigerant by adjusting the temperature of thecooling medium entering the second heat-exchanger to a value lower thanthe temperature of the chilled fluid leaving the first heat-exchanger;and conducting refrigerant condensed in the absorber to the evaporator;said steps being carried out with the generator and the condenserinoperative.
 6. The method according to claim 5, including the steps ofdiscontinuing circulation of the condensed refrigerant from the absorberto the evaporator; charging the absorber with absorbent solution,commencing operation of the generator and the condenser; and adjustingthe temperature of the cooling medium entering the second heat-exchangerto a value within the second range and higher than the temperature ofthe chilled fluid leaving the first heat-exchanger.
 7. In a method ofoperating a refrigeration system of the type having an evaporator, anabsorber, a generator, and a condenser connected in a closed circuitnormally conducting a refrigerant and an absorbent solution in anabsorption refrigeration cycle, the absorber being arranged in theclosed circuit to receive refrigerant vaporized in the evaporator andnormally to receive absorbent solution from the generator for absorptionof the vaporized refrigerant; means defining a chilling circuitcirculating a chilled fluid in heat-exchange relation with arefrigeration load and including a first heat-exchanger in theevaporator for abstracting heat from the fluid and rejecting it to therefrigerant to chill the fluid and to vaporize the refrigerant, thetemperature of the chilled fluid leaving the first heat-exchangernormally being maintained within a first range of values; means defininga cooling circuit circulating a cooling medium and including a secondheat-exchanger in the absorber for normally abstracting heat from theabsorbent solution and rejecting it to the cooling medium, thetemperature of the cooling medium entering the second heat-exchangernormally being maintained within a second range of values having anupper limit higher than the upper limit of the first range; and meansdefining a heating circuit normally conducting flow of a heating mediumand including a third heat-exchanger in the generator for normallyabstracting heat from the heating medium and rejecting it to theabsorbent solution; the steps of discontinuing operation of thegenerator and the condenser, and thereby interrupting the absorptionrefrigeration cycle, by discontinuing flow of the heating medium in thethird heat-exchanger; removing absorbent solution from the absorber andthe generator; operating the absorber to condense the vaporizedrefrigerant by adjusting the temperature of the cooling medium enteringthe second heat-exchanger to a value lower than the temperature of thechilled fluid leaving the first heat-exchanger; and circulatingrefrigerant condensed in the absorber to the evaporator.
 8. The methodaccording to claim 7, including the steps of discontinuing circulationof the condensed refrigerant from the absorber to the evaporator;returning the absorbent solution to the absorber and the generator;resuming operation of the generator and the condenser by resuming flowof the heating medium in the third heat-exchanger; and adjusting thetemperature of the cooling medium entering the second heat-exchanger toa value within the second range and higher than the temperature of thechilled fluid leaving the first heat-exchanger.
 9. In a refrigerationsystem including an evaporator and an absorber connected in a closedcircuit for normally conducting a refrigerant and an absorbent solutionin an absorption refrigeration cycle, the absorber being arranged in theclosed circuit to receive refrigerant vaporized in the evaporator andnormally being provided with absorbent solution for absorption of thevaporized refrigerant; means defining a chilling circuit for circulatinga chiLled fluid in heat-exchange relation with a refrigeration load andincluding a first heat-exchanger in the evaporator for abstracting heatfrom the fluid and rejecting it to the refrigerant to chill the fluidand to vaporize the refrigerant; and means defining a cooling circuitfor circulating a cooling medium and including a second heat-exchangerin the absorber for normally abstracting heat from the absorbentsolution and rejecting it to the cooling medium; means for operating theabsorber to condense the vaporized refrigerant, in the absence ofabsorbent solution in the absorber, when the temperature of the coolingmedium entering the second heat-exchanger is lower than a temperature ofthe chilled fluid which will satisfy the refrigeration load, thelast-mentioned means including bypass passage means communicating at oneend thereof with the absorber and at the other end thereof with theevaporator, and bypass valve means associated with the bypass passagemeans for controlling flow therein, the bypass valve means having anormally closed position and being movable to an open position for thecirculation of refrigerant condensed in the absorber to the evaporator.10. The combination according to claim 9, including refrigerantdistribution means in the evaporator for distributing unvaporizedrefrigerant over the first heat-exchanger; receptacle means in theevaporator below the first heat-exchanger for collecting unvaporizedrefrigerant; and refrigerant passage means connecting the distributionmeans and the receptacle means for conducting unvaporized refrigerantfrom the receptacle means to the distribution means; said other end ofthe bypass passage means communicating with the refrigerant passagemeans for circulation of condensed refrigerant from the absorber to thedistribution means when the bypass valve means is in its open position.11. The combination according to claim 10, wherein the refrigerantpassage means includes a refrigerant pump having an inlet incommunication with the receptacle means and an outlet in communicationwith the distribution means, the bypass passage means connecting theabsorber and the refrigerant pump inlet.
 12. The combination accordingto claim 11, wherein the bypass passage means includes an eductor havingan outlet, a suction inlet, and a motive fluid inlet, the eductor outletcommunicating with the pump inlet, the eductor suction inletcommunicating with the absorber; motive fluid passage means connectingthe pump outlet and the motive fluid inlet; and motive fluid valve meansbeing associated with the motive fluid passage means for controllingflow therein; the motive fluid valve means having a normally closedposition and being movable to an open position for operating the eductorto withdraw condensed refrigerant from the absorber when the bypassvalve means is in its open position.
 13. The combination according toclaim 9, including means for removing absorbent solution from theabsorber and comprising receiver means for storing the absorbentsolution, said receiver means having an inlet, receiver passage meanscommunicating at one end thereof with the receiver inlet, a solutionpump having an inlet communicating with the absorber and having anoutlet communicating with the other end of the receiver passage means,and receiver valve means associated with the receiver passage means forcontrolling flow therein, the receiver valve means having a normallyclosed position and being movable to an open position for removal of theabsorbent solution from the absorber to the receiver means.
 14. Thecombination according to claim 13, wherein said receiver means has anoutlet, second receiver passage means communicating at one end thereofwith the receiver outlet and at the other end thereof with the absorber,second receiver valve means being associated with the second receiverpassage means for controlling flow therein, the second receiver valvemeans having a normally closed position and being movable to an openposition for rEmoval of absorbent solution from the receiver means tothe absorber.